It has long been a desirable goal to deliver some kind of benefit agent (e.g., silicone or other oils) to the skin through a personal wash composition.
In liquid cleansers, for example, cationic hydrophilic polymers such as Polymer JR.RTM. from Amerchol or Jaguar.RTM. from Rhone Poulenc have been used to enhance delivery of benefit agents (EP 93,602; WO 94/03152; and WO 94/03151). In applicants' copending application, U.S. Ser. No. 08/412,803 to Tsaur et al., now abandoned, separate hydrogel particles act as a structure to entrap the benefit agent in concentrated form.
In the subject invention, entrapment of benefit agent is achieved by producing compositions comprising emollient wherein the medium in which the emollients are found (e.g., polyalkylene glycol) is thickened with a thickening agent (e.g., fumed silica) so that the droplets are entrapped in the polyalkylene glycol. More specifically, and without wishing to be bound by theory, the polyalkylene glycol is believed to act as a matrix entrapping the emollient and the thickener is believed to stop emollient from escaping from the matrix.
The emollient-containing thickened carrier compositions may be inserted into bars in concentrated forms (as in copending application U.S. Ser. No. 08/828,443 to Rattinger et al. filed on same day as subject application) or dispersed throughout the bar. The thickened carrier composition should be prepared separate from the base bar composition (and the separate chip compositions should be coextruded).
Delivery of benefit agents (e.g., silicone) in bar compositions has proven more difficult in bars for a number of reasons. If the benefit agent does not remain sufficiently discrete from other components in the bar composition, for example, the generally hydrophobic benefit agent can contact hydrophobic materials in the bar mix rather than deposit on the skin or other substrate. Thus, little or no benefit agent will be present in the final bar (after milling, plodding and extrusion of chips) to be delivered to the skin. If the benefit agent is too viscous, on the other hand, it tends to get in the processing equipment and become too difficult to process.
U.S. Pat. No. 5,154,849 to Visscher et al. teaches bar compositions containing a silicone skin mildness/moisturizing aid component. In one embodiment, the silicone component may be mixed with a carrier which is selected to facilitate incorporation of the silicone. Preferred carrier is said to be polyethylene glycol. At column 16, the reference describes that silicone is mixed into melted Carbowax (polyethylene glycol), that the mixture is cooled to form flakes, and that the flakes are preferably added to an amalgamator.
It is clear, however, that the Visscher et al. reference contemplates a silicone/carrier system different from the benefit agent/carrier/thickener system of the subject invention. First, the Visscher patent does not teach thickener (e.g., fumed silica or water soluble starch), a critical component of the emollient containing compositions and one which is believed to provide the structure required to retain and engulf the benefit agent (e.g., silicone) in the carrier. Second, as suggested above the structure of the carrier/silicone chip is distinct. The Visscher et al. composition does not contain the silicone in discrete droplets, but rather the silicone oozes and surrounds the carrier. By contrast, the benefit agent droplets of the invention are discrete droplets retained within the chip. This helps to ensure the silicone does not ooze and interfere with processing.
The discrete particles of the invention, in turn, are present for two reasons, it is believed. The first, as noted above, is presence of thickening agent (e.g. water soluble starch or fumed silica) which, while not wishing to be bound by theory, it is believed helps to thicken the carrier (e.g., PEG) such that the viscosity of the carrier is minimum 800 centipoise (cps), preferably greater than 1500 cps, more preferably greater than 3000 cps and can thereby entrap the silicone. The second reason is that, unlike the Visscher et al. system, the present invention requires there be an equal amount or more of carrier relative to the benefit agent. By contrast, it appears from Visscher et al., where eleven pounds of silicone (column 15, lines 1-2), are mixed with 5 to 6 pounds of Carbowax (column 15, line 29) that there is probably an excess of silicone to PEG and, at the least, there is no recognition of the criticality of having an equal amount or more of PEG to silicone.
In short, the chips of the Visscher reference are extremely difficult to process both because there is no control over the amount of silicone used and because there is no use of thickened carrier.